Syringomyelia
What is Syringomyelia?
Syringomyelia is a fluid-filled cavity located within the spinal cord, the lower part of the central nervous system that continues down the brain stem and extends from the craniocervical junction to one of the first lumbar vertebrae (L1 or L2), and is made up of a series of cervical, dorsal and lumbar segments, which receive sensory information from the periphery through the posterior (dorsal) roots of the spinal nerves and send motor information to the muscles of the trunk and limbs through the anterior roots. Syringomyelia can be a congenital or acquired pathology.
According to the hydrodynamic theory, the Chiari malformation would compromise the outflow of CSF from the posterior fossa, which in turn would produce a pressure wave directed toward the ependymal canal and its consequent dilatation. Other malformations associated with syringomyelia include tethered medulla syndrome, Klippel-Feil syndrome and basilar invagination, among others.
Acquired syringomyelia may occur in association with various spinal cord diseases, including trauma, infection, non-infectious myelitis, hemorrhage and trauma. In these cases the location and extent of the cavity is highly variable, depending on the underlying cause. As in congenital forms, acquired syringomyelia may produce delayed symptoms, even years after the initial event.
What are the symptoms of syringomyelia?
The symptoms of syringomyelia will depend mainly on the location of the cavity, both in the longitudinal direction (cervical, dorsal or lumbar segments) and in the transverse plane (medullary gray matter or anterior, lateral or dorsal cords).
Syringomyelia is often an imaging finding (incidental lesion) and does not produce significant symptoms, so in these cases it is usually decided to monitor the evolution. However, symptomatic cases usually present with pain and localized sensory and motor symptoms at the level of the medullary segments corresponding to the cavity.
Congenital forms most frequently affect the cervical segments and central regions of the spinal cord, causing cervical pain, loss of strength and sensation in the upper limbs (arms), with particular impairment of sensitivity to touch, pain and temperature (“suspended deficit”).
In more advanced cases the lesion may affect the long pathways located in the white matter cords, resulting in the appearance of sensory and motor symptoms in the lower limbs (legs) and autonomic problems (e.g. alterations of sphincter control and sexual function). In childhood-onset cases, scoliosis is also frequently associated.
How is syringomyelia diagnosed?
Currently the procedure of choice for the diagnosis of syringomyelia is magnetic resonance imaging (MRI). Since syringomyelia is often associated with congenital malformations or lesions at other levels of the nervous system, it is advisable to perform a complete study of the neuroaxis.
In some centers conventional MRI is complemented with sequences aimed at analyzing CSF flow at the posterior fossa level (cine-MRI). In acquired forms, post-contrast sequences are usually obtained in order to detect underlying lesions (such as tumors or inflammatory processes).
In cases where MRI is not possible (e.g. cardiac pacemakers not compatible with MRI), spinal computed tomography (CT) can be performed, often combined with CSF contrast injection (myelo-CT).
What is the treatment of syringomyelia?
The treatment of syringomyelia depends on the underlying cause, but whenever possible, etiological treatment aimed at correcting the cause should be performed. This recommendation is especially valid for acquired forms such as those associated with tumors or infections.
In congenital cases associated with Chiari malformation, several therapeutic procedures are available, the choice of which depends on the patient’s symptoms and the experience of the medical team. Also, when the Chiari malformation is an incidental finding, most experts recommend clinical and radiological follow-up. However, when it presents with syringomyelia and a complete blockage of CSF flow is detected by cine-MRI, some specialists recommend surgical treatment to prevent the development of neurological problems. In fact, the absence of significant blockages in symptomatic patients is predictive of poor response to treatment.
The goals of Chiari malformation treatment are to decompress the posterior fossa and the craniocervical junction and to restore CSF flow at these levels. Regarding the available methods, the most commonly used is posterior decompression by means of a suboccipital craniectomy with opening of the dura. The main complications of this procedure include the formation of a fluid cavity at the surgical site (pseudomeningocele), CSF fistulas, postoperative hydrocephalus and peri-surgical infections (meningitis and wound infections).
Some surgeons opt for more conservative procedures (craniectomy without opening the dura). In general, these procedures produce fewer side effects, but appear to increase the risk of recurrences and the need for further interventions. Other less commonly used treatments include anterior decompression of the foramen magnum and insertion of a shunt into the syringomyelic cavity. These techniques are usually used as a second-line treatment when suboccipital craniectomy has failed.
What is the prognosis of syringomyelia?
The prognosis of acquired forms is highly variable, depending to a great extent on the pathology responsible and its treatment possibilities.
In particular, the prognosis of cases associated with Chiari malformation cannot be predicted with certainty, so it is essential to closely monitor their evolution. In general, the available data suggest that most asymptomatic or mildly symptomatic patients remain stable and, in fact, spontaneous resolution of tonsillar descent and syringomyelia has even been described.
On the other hand, follow-up of patients treated with surgery suggests that most of them remain stable or improve in the following years. In the surgical series, the main data of poor prognosis consist of advanced age and long tract involvement at the time of surgery. Between 5% and 10% of cases require reintervention, which may consist of a new posterior fossa decompression or the implantation of a shunt in the syringomyelic cavity.
Where can I find additional information about syringomyelia?
For more information on this pathology we recommend accessing the corresponding page of the US National Institute of Neurological Disorders and Stroke (NINDS): https://espanol.ninds.nih.gov/trastornos/siringomielia.htm
Additional information about this disease and the resources available in our country can also be obtained through the associations of patients (www.siringomielia.o; http://arnoldchiari.es; ascenycasociacion@gmail.com).
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